LiGa(IO₃)₄: An Excellent NLO Material with Unprecedented 2D [Ga(IO₃)₄]_∞⁻ Layer Synthesized by Aliovalent Substitution

Abstract Nonlinear optical (NLO) crystals are indispensable for the solid‐state lasers for their ability to expand wavelength spectral to the regions where the directing lasing is difficult or even impossible, yet the rational design of a high‐performance NLO crystal remains a great challenge owing to the severe structural and properties’ requirements. Herein, a new noncentrosymmetric (NCS) and polar gallium iodate, LiGa(IO₃)₄, with a novel 2D anionic layer, is successfully designed and synthesized by the aliovalent substitution strategy based on classic α‐LiIO₃. The 2D [Ga(IO₃)₄]_∞⁻ layer in LiGa(IO₃)₄ is built from the GaO₆ octahedra and highly polarizable units IO₃. Compared with its parent compound, the partial replacement of A‐site Li⁺ cation with main group Ga³⁺ cation facilitates LiGa(IO₃)₄ to possess excellent NLO properties, including the large second‐harmonic generation (SHG) response (14 × KH₂PO₄ (KDP) @ 1064 nm), wide bandgap (4.25 eV), large birefringence (0.23 @ 1064 nm), and wide optical transparency from UV to mid‐IR. These reveal that LiGa(IO₃)₄ will be a promising NLO crystal.